Hydrodesulfurization and hydrogenation with platinum-eta alumina catalyst



United States Patent HYDRODESULFURIZATION AND HYDROGENA- WITHPLATINUM-ETA ALUMINA CATA- i No Drawing. Filed Feb. 1, 1956, Ser. No.562,660

4 Claims. (creas -217) This invention concerns a novel process forupgrading petroleum fractions boiling in the range of about 300 to 650F. in a hydrogenation process by the selective hydrogenation of aromaticcompounds. The invention is of particular application for processingvirgin stocks, but is also applicable and of value in improvingcatalytically cracked stocks. While this selective hydrogenation ofaromatic compounds is valuable for treatment of a number of stocks, thisprocess is of particular value for improving the burning qualities ofkerosene, diesel fuel, jet fuel, and fuels for gas turbines.

In accordance with this invention, petroleum fractions containingaromatic hydrocarbons boiling in the range of about 300 to 650 F. arehydrogenated at temperatures of about 500 to 675 F., a pressure of about100 to 1,000 p.s.i.g., in the presence of about 2000 to 15,000 standardcubic feet of hydrogen per barrel of feed, preferably 5,000 to 8,000standard cubic feet of hydrogen per barrel of feed, specificallyemploying a catalyst consisting of platinum supported on eta alumina.The invention resides in use of this particular catalyst at specifichydrogenation conditions with selected feed stocks so as to obtainunique product quality improvements. As indicated, while the inventionis of value in the treatment of a variety of feed stocks, it will bedescribed with particular reference to the treating of diesel fuels andkerosenes, including jet fuels and gas turbine fuels.

In the case of diesel fuels and kerosenes, for example, the ignitioncharacteristics and burning characteristics respectively are ofparticular importance from the viewpoint of product quality. Thesecharacteristics are often controlling in refining operations,necessitating specific techniques for improving these properties ofthese stocks. Burning characteristics of a kerosene may be measured bysmoke point tests which can readily be carried out by determining theheight of flame obtainable at incipient smoking, With the aim being toobtain kerosenes having the highest values of smoke point. The ignitioncharacteristics of diesel fuels which are pertinent to this inventtioncan be determined by cetane number inspections. These properties of thefuels identified are each dependent on the aromatic content of the fuel.Thus, both kerosene and diesel fuels, which are highly aromatic, arenormally deficient in the aforementioned characteristics. To a lesserdegree, these characteristics are also related to, and affected by, thenaphthene content of the fuel. For these reasons, the present inventionis particularly aprange of about 300 to 650 F. containing at least andup to about 50% of aromatic hydrocarbons and having a naphthene ringcontent of less than about 30%. More specifically, the invention is ofparticular applicaplicable to petroleum fractions boiling within aboiling 2 tion to virgin kerosenes boiling in the range of about 300 to500 F., and to virgin or cracked diesel fuels boiling in the range of300 to 625 F. This process, is however, applicable but somewhat lessefficiently, to feeds containing less than 10% and more than 50% ofaromatic hydrocarbons.

In order to improve the burning properties of these fuels, it isnecessary to hydrogenate selectively the aromatic compounds present. Itis, of course, preferable to obtain complete conversion of all aromatichydrocarbons, although conversions above about and particularly above98% are effective for substantially upgradingthese fuels.

The present invention is based on the provision of a suitable processfor the conversion of aromatic hydrocarbons present in such stocks askerosenes and diesel fuels. covery of a catalyst and conditions forusing this catalyst which attains the unique objectives which areinvolved in this problem. These and other features of the invention willbe brought out in the description of the invenion which follows:

In order to establish the nature and advantages of this invention,reference will be made to some of the critcial features involved inupgrading kerosenes and diesel fuels. As a starting point, it must beappreciated that unusual problems are involved in providing ahydrogenation process suitable for hydrogenation of aromatichydrocarbons while preventing other undesirable results such ashydrocracking. In this connection, in a first step of thestudy on whichthis invention is based, a wide variety of hydrogenation catalysts whichhave proved of value in other types of hydrogenation were evaluated foractivity in hydrogenating aromatic compounds. In the specific testsreferred to, a low sulfur kerosene derived from Sweden crude wasemployed. Standard hydrogenation conditions were selected for testingeach of the catalysts, and theseconditions were a pressure of 800p.s.i., a temperature of 600 F., and a throughput of 4 v./hr./v.

A commercially available cobalt molybdate alumina catalyst of the naturenow used in commercial hydrofining operations was first tested. Whilethis catalyst has excellent activity for conversion of sulfuf compounds,and for saturation of olefinic compounds, this catalyst was found tohave no activity for the conversion of aromatic hydrocarbons under theconditions of this test. Other catalysts such as a commerciallyavailable platinum on alumina catalyst, a commercially available rhodiumon alumina catalyst, and other experimental catalysts were found to havesubstantially no activity for the hydrogenation of aromatic nuclei. Onecatalyst found to have good activity for this purpose was a commerciallyavailable nickel catalyst supported on kieselguhr. However, this nickelcatalyst exhibited rapid and serious deactivation in use.

As a result of such studies, it has been found that platinum supportedon eta alumina exhibits unique properties for the hydrogenation ofarmoatics. The catalyst constitutes about 0.001 to 5% of platinumsupported on the particular form of alumina known as eta alumina. As nowknown to the art, eta alumina may be produced by heating alumina betatrihydrate at temperatures of about 500 to 1400 F. In accordancewith'this invention, this particular catalyst is used for treatingpetroleum fractions containing aromatic hydrocarbons.

A particular feature of the invention is the dis- The catalyst used inthis invention may be prepared in the following manner.

One method of preparing eta alumina is to hydrolyze aluminum alcoholatewith an aqueous solution containing ammonium hydroxide. The aluminumalcoholate may be prepared in any suitable manner. One method ofpreparation of aluminum alcoholate is given in Kiberlin U.S. Patent No.2,636,865. ,Aluminum alcoholate is hydrolyzed with good agitation withfrom about 1 to 10 volumes of ammonium hydroxide per volume of aluminumalcoholate, preferably two to three volumes of ammonium hydroxide pervolume of aluminum alcoholate, the concentration of NH being in therange of about 1.8 to 3.4 weight percent. The temperature of hydrolysisis preferably kept within a range of about 35 to 100 F. Upon hydrolysis,an alumina slurry is obtained and this slurry is aged for a period ofone to 15 hours, preferably 3 to 8 hours at room temperature. The agingis preferably carried out in the range of about 35 to 80 F.

The alumina slurry contains alumina in the beta trihydrate form and theslurry is first dried at a temperature of about 200 to 400 F. to removethe ammonia and water to recover dry alumina. Crystalline eta alumina isformed by further dehydrating the beta alumina trihydrate and it hasbeen found that the conversion to the eta form is essentiallyquantitative when the activating temperature is in the range of about450 to 1100 F. The activation is generally in the presence of air butcan be done in the presence of inert gases.

The eta alumina is used as a support for platinum and is impregnatedwith an aqueous solution of water soluble inorganic platinum containingcompounds such as chloroplatinic acid, platinum sulfide, etc. The termWater soluble also includes platinum-containing compounds which formcolloidal solutions.

A preferred solution is one containing 15 grams of H PtCI JcH O (40% Pt)per liter. This strength of solution can be employed to yield catalystscontaining about 0.6% platinum but the strength of the solution may bevaried to obtain a catalyst containing about 0.001 to 5% platinum byweight. The alumina support is impregnated with the platinum solution,is then heated to dryness, con veniently at temperatures of about 100 to600 F., preferably about 250 F., at atmospheric pressure and thisresults in removal of a substantial portion of the water. Thereafter thecatalyst is calcined at a temperature between about 800 and 1250 F.,preferably about 1100 F. The calcining step is preferably carried outfor about 1 to 24 hours.

Before impregnating the eta alumina base with the platinum compound, itis also within the contemplation of this invention to calcine the etaalumina and this can be done at a temperature between about 800 and 1600F., preferably about 1100 to 1500 F., for 1 to 24 hours. In some casesit is also desirable to treat the platinum catalyst or the eta aluminabase either before or after calcination with an aqueous dilute mixedacid solution such as one containing nitric acid, perchloric acid, orhypochlorous acid, together with a hydrogen halide such as HCl, HF, HIand HBr The mixture containing nitric acid and hydrochloric acid ispreferred. An amount of nitric acid based on the total catalyst of about0.1 to 8 weight percent on the total catalyst is preferred. The HCl isemployed in an amount of about 1 to 30 weight percent based on the totalcatalyst. The nitric and hydrochloric acids are contained in about 50 to500 Weight percent of water on the total catalyst.

In acid treating the catalyst, the catalyst is mixed with the acidsolution, heated on a steam bath at about 150 to-180 F. for at least onehour, the acid solution is then drained off and the catalyst is Washedthoroughly with distilled water. The washed catalyst is then dried atabout 250 F. and recalcined for about 1 to,4 hours at between about 800and 1250 F., preferably about 1100 F.

In a specific example, the alumina support for a catalyst was obtainedby hydrolysis of aluminum alcoholate solution by the method discussedabove. The alumina after drying at about 250 F. was pulverized to passthrough a 20 mesh screen and was then heated and activated at about 1100F. for about 4 hours. To each 100 grams of activated alumina was added asolution made by dissolving 1.5 grams of H PtCl (40% platinum) in aboutcc. of distilled water. The composition Was well mixed and driedovernight at room temperature. The catalyst was then dried at 250 F.,screened and pilled. The pilled catalyst was calcined for 1 hour atabout 1100 F.

The pilled and calcined catalyst was then treated with a solutioncontaining 7 weight percent on catalyst of concentrated HCl and 4 weightpercent on catalyst of concentrated HNO and 200 weight percent oncatalyst of distilled water. The catalyst pills were'slurried in theacid solution on a steam bath-for about one hour. The temperature of thesolution was about 150 to 190 F. The acid solution was then drained ofiand the catalyst washed with distilled water. The washed catalyst wasdried at 250 F. and calcined at 900 to 1100 F. for one hour.

In a first experiment conducted, a platinum on eta alumina catalyst notacid treated, was employed in the hydrogenation of a xylene fractionconstituting mixed xylenes, although predominating in meta xylene. Atemperature of 615 F., a pressure of 400 p.s.i.g., a feed rate of 1v./v./hr. and 7000 cubic feet of hydrogen per barrel of feed wereemployed. obtained showed a 96% conversion of the mixed xylenes todimethyl-cyclo hexanes and tri-methyl cyclo pentanes. Other experimentsconducted with substantially pure aromatic hydrocarbons boiling in therange of about 430 to 650 F., supported these results in showing thepracticality of hydrogenating aromatic hydrocarbons with this specificcatalyst.

Other tests which were conducted to demonstrate the process of thisinvention employed a commercial kerosene having the inspections shown inTable I.

TABLE I Kerosene inspections Gravity, API 42. 6 ASTM Distillation Secific Gravit 60 50 0.813 Percent Tern p y I O.H. Aniline Point, F 148TB? 319 Smoke Point, mm 21. 5 10 382 FIA, vol. percent 20 400Aromatics... 17 805.9) 30 414 Ole 51 S 5. 3 40 425 Satu "ates 76. 9 50435 Sulfur. Wt. perce 0.023 60 445 Bro "nine 310., cg. Brz.'gu1.. 1.77456 Refractiverlndor, 20 C./D 1. 4490 469 Viscosity at 30 F., cs. 11.2484 Freezing Point, F. -42 498 Flash Point, F 134 FBP 516 A variety oftests for the hydrogenation of this kerosene and additional tests forthe hydrogenation of xylene, are summarized in Table II. These testswere conducted in a continuous hydrogenation operation at a pressure of400 p.s.i.g., and 0.8 to 1.0 v./hr./v., employing aplatinum on etaalumina catalyst containing 0.6% of platinum which was diluted with anequal amount of tabular alumina. Temperatures of 500, 600 and 675 F.were studied and hydrogen dilutions ranging between It was found thatthe product 6,000 to 7,500 standard cubic feet per barrel were employed.Table II summarizes the results of these tests:

TABLE II Hydrogenation of aromatics over platinum on em alumina catalyst[0.6% Pt. on 41-0,; 400 p.s.i.g.]

Retractive FIA Feed Hour on Feed Temp., VJHrJV. Hg, Index Smoke F.S.C.F./Bbl 20 CJD Pt.,mn1.

Arorn Olefins Sets.

1.4951 100 0 610 1. 3. 0 1. 428s 28.0 5. 4 1.5 93.1 Xylene 1 510 0. 907. o 1. 4258 31. 5 2. 4 1. 7 95. 0 675 0. 90 5. 5 1. 4295 24. 0 9. 4 2.3 ss. 3 1. 4490 21. 5 17.8 5. 3 76.9 500 0.95 5. 0 1. 4407 29. 0 10. 75. 5 83.8 500 0. 92 6. 0 1. 4424 25. 5 14. 0 2. 7 s3. 3 600 0. 9s 6.0 1. 4438 27. 0 13. 4 a. 5 e3. 1 675 0. s9 5. 0 1. 4440 25. 0 15. s a. 0s1. 2

500 1. 00 5. 0 1. 4412 28.0 11.2 2.1 35. 7 575 0.80 7. 0 1. 4435 25. 515. s 2. a s1. 4 575 0. 86 5. 5 1. 4441 24. 0 15.8 3. 5 s0. 5 575 0. 906. 5 1. 4440 24. 0 15. 1 2. 6 s1. 3 Kerosene 12 575 "13. 55' 5.5 1.444724.0 16.3 3.3 80.4 675 0.86 6.5 1.4450 500 0. 90 6. 5 1. 4417 28. 0 10.9 3. 9 85.2 500 0. 55 5.5 1.4440 500 0. 91 5. 5 1. 4441 27. 0 14. 5 5. 2so. 2

1 Malllnclcrodt A. R. Xylene, 0.003% S.

1 Inspections, Table I I Alternate feed H strip min.

4 Alternate feed 10 mln., H, strip 5 min.

H3, 900 F., 3 Hours.

. Referring to the data of Table II, it will be seen that maintainedduring the hydrotreating process; that is, in every run reported,substantial conversion of aromatic 4 about 200 to 1000 p.s.i. g.

compounds was obtained. However, the data shows that 0 Alternatively, anoxidative regeneration may be conparticularly good results were obtainedin hydrofinishing ducted. In this case the catalyst is first purged ofhydrokerosene at 600 F., serving to reduce aromatics from carbonsemploying an inert gas such as nitrogen. There- 17.8% to 8.7% andimproving smoke point from 21.5 after air diluted with nitrogen or otherinert gas is conrnm. to 30.5 mm. Included in Table II are datashowtacted with the catalyst to secure combustion of caring the effectof regenerating the catalyst used in a hy- 45 bonaceous deposits on thecatalyst while holding the temdrogen regeneration treatment. It is shownthat contact perature below about 1050" F. After an initial period ofspent catalyst with hydrogen at 900 F. for three of regeneration withdilute air, the oxygen content may hours is effective for regeneratingthe catalyst. Also, as be increased to that of undiluted air, preferablyincluding shown by hours 20 to 22, however, intermittent hydroexposureof the catalyst to air at about 950 F. to 1175 gen stripping at 600 F.is also particularly elfective in F. at reaction pressure for an hour ormore, preferably maintaining good catalyst activity. four or more hours.

These and other tests which were conducted establish As described, theprocess of this invention concerns that platinum on eta alumina catalystmay be used in the the hydrofinishing of petroleum fractions for productprocess of this invention at temperatures in the range qualityimprovement by the conversion of aromatic hyof 500 to 675 F., with about600 F. being a preferred drocarbons. The invention has been describedwith temperature for operation. Non-regenerative operations particularreference to the treatment of diesel fuel in may be conducted attemperatures in the upper portion kerosene, but is also of applicationin the treating of of this range, particularly when employingintermittent jet fuels and gas oils. In the latter connection, forexhydrogen stripping which may be conducted by periodiample, thehydrotreating process of this invention can cally cutting offhydrocarbon feed at intervals of about 5 desirably be used for theupgrading of catalytic cracking to 180 minutes. Hydrogen stripping willbe carried out feed and. cycle stocks by conversion of the aromatic hyatabout 500 to 800 F., preferably for about 5 to 60 drocarbons present insuch stocks. minutes. However, somewhat lower temperatures better Whilethe invention has been described with particufavor aromatic conversion,although necessitating regenlar reference to fixed bed operation, it isapparant that eration of the catalyst. Pressures to be employed in thisthe fluidized technique or moving bed principles may be invention areselected from the broad range of 100 to employed. Again, while theinvention has been described 1000 P- although pressures of about 200 to400 as a single stage treatment with platinum on. eta alumina, p.s.i.g.are preferred. Use of higher pressures in the staged operations orcombinations with other treating range stated are favorable foraromatics conversion. processes may be used. For example, in the case ofhigh As stated, the present invention may be conducted as sulfur contentfeed stocks, it may be desirable to emeither a non-regenerative process,or a regenerative ploy a desulfurization step prior to the use of theprocess. Conventional techniques for catalyst regeneraprocess of thisinvention. Hydrodesulfurization using a tion may be employed. Thepreferred procedure, howcatalyst such as cobalt molybdate can desirablybe used i5 to p y g temperature y g regenera' for this purpose. Theseand other variations and modifition entailing hydrogen contact with thecatalyst at a cations of the invention may be employed.

- swwsa i 7 What is claimed is: g 1. A process for upgradingetroleum"fractions containing aromatic and sulfur compounds boiling in the rangeof about 300 to 650 R, which consists of hydrogenating said fractions toobtain substantial hydrogenation of aromatics and removal of sulfur ata"temp'erature of about 500 to 675 F., at a pressure of about 100 to1000 p.s.i.g., in the presence of about 5,000 to 8,000 standard cubicfeet o'fhydrogen"perbarreloffeed in contact with a catalyst comprisingplatinum supported on eta alumina.

2. The process'defined by cla-im 1 in which the said petroleum fractionis selected "from the group consisting of kerosene, diesel fuel, gasoil, and jetfuel.

3. The process defined'by claim 1 in which the-said catalystcontains-0.001 to-5.0% ofplatinum.

"'4. The proces 'defin'd byblai mdin wfliehthe saiii catalysfcontains0.05'to 1.0%"platir'1'um.

"References Cited in the file of this patent UNITED STATES PATENTS v. 1rank

1. A PROCESS FOR UPGRADING PETROLEUM FRACTIONS CONTAINING AROMATIC ANDSULFUR COMPOUNDS BOILING IN THE RANGE OF ABOUT 300* TO 650*F., WHICHCONSISTS OF HYDROGENATING SAID FRACTIONS TO OBTAIN SUBSTANTIALHYDROGENATION OF AROMATICS AND REMOVAL OF SULFUR AT A TEMPERATURE OFABOUT 500* TO 675*F., AT A PRESSURE OF ABOUT 100 TO 1000 P.S.I.G., INTHE PRESENCE OF ABOUT 5,000 TO 8,000 STANDARD CUBIC FEET OF HYDROGEN PERBARREL OF FEED IN CONTACT WITH A CATALYST COMPRISING PLATINUM SUPPORTEDON ETA ALUMINA.